This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Sweden Application No. 0001827-5 filed on May 18, 2000, the entire content of which is incorporated herein by reference.
1. Technical Field of the Invention
The present invention relates to a tool coupling for stationary metal cutting tools, preferably for turning tools. The tool coupling couples together a holder and a tool body which is intended to carry (or by itself constitute) a cutting insert for chip removing machining. The tool coupling comprises a male part, which has a first center axis, and a female part, which has a second center axis. The male part and female part are intended to be received one in the other. The invention also separately relates to a cutting insert for chip removing machining.
2. Prior Art
A replaceable cutting body, i.e., a so-called loose top, that is attached to a shaft is previously known from DE-OS 34 02 547. The tool in question is especially suited for internal turning. The connection between the cutting body and the shaft is formed in such a way that three radial grooves are formed in the end of the shaft facing the cutting body, while three radial ridges are arranged on the cutting body. In the active position of the connection, an axial screw extends through the cutting body and into the shaft, the ridges being received in the grooves. Thereby, a torque may be transferred from the shaft to the cutting body. By virtue of a relatively flat inclination of the co-operating flanks of the grooves and the ridges, a relatively high axial force is required between the shaft and the cutting body in order to transfer torque of the magnitude desired from the shaft to the cutting body. The high axial force may lead to an elongation of the screw. Furthermore, it is difficult to define where abutment between the ridges and grooves will take place since the ridges and grooves have a linear extension.
Aims and Features of the Invention
A primary aim of the present invention is to provide a tool coupling of the kind defined in the introduction, the tool coupling being capable of transmitting large torques or restraining force.
Another aim of the present invention is that also at a moderate axial prestress, there is an exceptionally small risk of failure of the transmission of torque.
Yet another aim of the present invention is that the tool coupling should be self-centering.
An additional aim of the present invention is that the tool coupling is free of play according to one embodiment.
At least the primary aim of the present invention is realized by the combination of a stationary metal cutting tool holder and a mounting body therefor. The tool includes a body having at least one seat for receiving a cutting insert. A securing element secures the tool holder to the mounting body. The tool holder includes a first coupling part defining a center axis. The mounting body includes a second coupling part arranged coaxially with the first coupling part. The first and second coupling parts are conical as viewed in a longitudinal sectional plane containing the axis, and are arranged one inside of the other. The first coupling part includes teeth spaced circumferentially apart about the axis and projecting generally radially with respect to the axis. The teeth are received in respective radially open circumferentially spaced recesses formed in the second coupling part. Each of the teeth terminates in an axially facing wall and includes a sidewall contacting a sidewall of the respective recess. A curvature of the tooth sidewall is different from a curvature of the recess sidewall at locations where those sidewalls contact one another. Such contact is in the form of a point contact on each side of a generally radial line of symmetry of the respective tooth as viewed in a direction parallel to the access. Each of the contact points is operable to transmit a restraining force from the second coupling part to the first coupling part in a respective direction. Each of the contact points defines a tangent line, wherein the restraining force is transmitted along a line of force oriented perpendicular to a respective tangent line. A restraining angle in the range of xe2x88x925xc2x0 to +45xc2x0 is formed between the bisector and a line extending perpendicular to the line of force.
The invention also pertains to a metal cutting insert for chip removing machining. The insert includes a body having a top surface with an integral cutting edge, and a bottom surface with an integral coupling part. The coupling part defines a center axis and is conical as viewed in a longitudinal section plane containing the axis. The coupling part includes a plurality of teeth spaced circumferentially apart about the axis and extending generally radially with respect to the axis.